Insertion is done successfully but the record is not shared to the corresponding user.Please help 
 
 
//This class is used for manual sharing of Case Record
public class ManualSharingRecord {
   
    //This method takes two parameter first the record ID which you want to share
    //and second one to whom you want to share the record(Either user or group)
    public static Boolean successfullCaseSharing(ID recordId,ID userORGroup)
    {
        //create the object of caseshare object type
        CaseShare csShare=new CaseShare();
       
        //set the record level of sharing
        csShare.CaseAccessLevel='edit';
        //put the recordId which you want to share
        csShare.CaseId=recordId;
        system.debug('Record Id'+ csShare.CaseId);
        //put the userORGroup id to whom you want to share the record
        csShare.UserOrGroupId=userORGroup;
                system.debug('userId'+csShare.UserOrGroupId);
       csShare.RowCause=schema.caseShare.RowCause.manual;
       
        Database.SaveResult save=Database.insert(csShare,false);
        {
            if(save.issuccess())
            {
                return true;
            }
            else
            {
                Database.Error err=save.getErrors()[0];
                system.debug('Error'+save.getErrors()[0].getMessage());
                if(err.getStatusCode()==statuscode.FIELD_FILTER_VALIDATION_EXCEPTION &&err.getMessage().contains('Accesslevel'))
                {
                    return true;
                }
                else
                {
                    return false;
                }
                   
            }
        }
       
        
      
    }
 
}
 
 
 
case cs=new case(status='new',origin='phone');
    insert cs;
ID recordId=cs.id;
User us=[select id from user where name like '%abc%'];
ID userORGroup=us.id;
boolean rs=ManualSharingRecord.successfullCaseSharing(recordId, userORGroup);
system.debug('result'+rs);